The detection of spread spectrum signals and signal traffic may be useful for a variety of different purposes. For example, the operation of certain wireless systems may be adjusted depending on whether they are handling signal traffic or not. However, there is an inherently difficult problem in determining the existence of spread spectrum signals for the purpose of making decisions about the operational parameters of a wireless system. In spread spectrum technology, the signals are subject to spreading codes, which are often called “Pseudo Noise” (PN) codes. Because of the noise-like structure of the signals, they are difficult to detect when the spreading codes are not known. Generally, in certain applications, the system will not have knowledge of the codes of the spread spectrum signals that it processes. As such, it becomes difficult to detect the signals or to adjust the operational parameters based on such signal detection.
One particular wireless system that might benefit from such signal detection is a system using one or more repeaters. In existing wireless technologies, signal repeating devices, or “repeaters” are used to extend the coverage of an overall wireless or cellular system. For example, often such wireless or cellular systems include a plurality of base stations or base transceiver stations (BTS) that communicate with each other. The BTS operate in an overlapping fashion to provide a defined signal coverage area for user equipment (UE), such as a cell phone or other wireless device. In such coverage areas, there are often smaller, more remote areas that have very low signal reception, such as areas within buildings or areas that are otherwise obstructed. Rather than implementing another costly and large base station to provide coverage to such low signal areas, signal repeating devices or repeaters are utilized.
A repeater operates with one or more adjacent BTS or other signal sources and increases usable signal coverage to the low signal areas. A repeater has a donor antenna that is in communication with the one or more BTS. The repeater receives downlink signals from the BTS or other signal source, processes and amplifies those signals, and then transmits or repeats the received signals through a coverage antenna into the remote area that otherwise has low signal reception or low signal power. An uplink signal from another signal source, such as a cellular phone or other UE, is similarly repeated in the uplink direction.
For example, referring to FIG. 1, a portion of a wireless communication system 10 might include a base station or BTS 12 or other signal source that communicates with a repeater 14 having a donor antenna 16, a coverage antenna 18, and processing electronics 20 that are configured to process and amplify the repeated signal. Accordingly, downlink wireless signals 22 from the BTS 12 are received by the donor antenna 16 of the repeater. The downlink signals are then amplified and transmitted through the coverage antenna 18 as repeated downlink signals 22a. The repeated downlink signals 22a are transmitted into the remote area and are received by the UE that may include one or more wireless communication devices, such as cell phones 24, as shown in FIG. 1. Similarly, in an uplink direction, as indicated by reference numerals 26 and 26a, the UE devices 24 or other signal sources communicate signals 26a back to the coverage antenna 18, and the signals 26a are then transmitted as repeated uplink signals 26 back to the BTS 12. As would be readily understood by a person of ordinary skill in the art, such repeater devices 14 can take many different forms.
One particular performance characteristic of a repeater is the operational gain of the repeater, or the amount of amplification that the repeater applies to the repeated signal. In many applications of a repeater within a wireless system, it is desirable to vary the gain of the repeater based upon signal traffic and signal transmission parameters. For example, in a spread spectrum system, such as a CDMA system that utilizes spread spectrum signal traffic, it may be desirable to decrease the gain of the repeater based upon the absence of any spread spectrum signal traffic through the repeater. Otherwise, a repeater that continuously operates at a high gain will increase the interference level within the wireless coverage area.
As noted, spread spectrum signals appear generally noise-like in structure and are thus susceptible to the overall noise figure within the wireless system. Therefore, the overall network capacity within a spread spectrum communication network is a function of the interference or noise level within that wireless network. As such, it is desirable to automatically adjust the gain, and specifically decrease the gain when there is no signal traffic through the repeater. Conversely, when spread spectrum signal traffic is present, it would be desirable to increase the repeater gain for better signal to noise performance.
There is an inherently difficult problem in automatically controlling the gain of a repeater within a spread spectrum system based upon the existence or absence of spread spectrum signal traffic due to the noise-like structure of the signals. A repeater will not have knowledge of the codes of the spread spectrum signals that it repeats. As such, it becomes difficult to automatically adjust the gain of a repeater based upon such signal detection.
Accordingly, there exists a need in the art to detect spread spectrum signals provide gain control within a repeater, and particularly to provide gain control for a repeater in a network utilizing spread spectrum signals.